Sterilizing solution



Patented Dec. 17, 1935 UNITED STATES STERILIZING SOLUTION Lamont J. Benson, New Kensington, Pa., assignor to Aluminum Company of America, Pittsburgh, Pa, a corporation of Pennsylvania No Drawing. Application April 14, 1932,

Serial No. 605,357

5 Claims.

This invention relates to sterilizing solutions which may be safely used to sterilize metal parts without seriously corroding or staining the metal. The invention is particularly directed to the provision of sterilizing solutions which contain, as

an active sterilizing component, available chlorine. It refers in this preferred form to the sterilization of aluminum articles. Sterllizing compositions which have, in solution, available 1o chlorine are preferred in most sterilizing work,

such as in connection with dairy equipment.

Since the article to be treated is quite often metallic, the metal may be corroded unless the formation in the sterilizing solution of corrosive 15 compounds or substances is prevented. Toward this end it has been proposed that a metasilicate of an alkali metal be dissolved in the solution to prevent hydrolysis and to alkalinize the solution, and to thus prevent the consequent formation of corrosive chlorine compounds, such as hypochlorous acid.

In sterilizing aluminum vessels with solutions containing available chlorine and alkali metal a metasilicate I have noted that the solution stains and corrodes the aluminum and is not satisfactory for use therewith. On further investigation I have determined that alkali metal metasilicate (R2O.S1Oz) does not have the desired effect ascribed to it when present in solutions containing available chlorine and that, regardless of its presence, corrosion of the metal takes place.

I have discovered that the efiects ascribed to the alkali metal metasilicate are not obtained by its use and that such effects are only obtained when there is. used alkali metal di-silicate (R20.2Si02). Alkali metal di-silicate will, when present in sterilizing solutions containing available chlorine, effectively stop the corrosive attack of the solution, and solutions containing the disilicate are particularly useful in the sterilization of aluminum. The present invention comprises, therefore, the provision of a sterilizing solution which contains available chlorine and alkali metal di-silicate such as sodium disilicate or potassium disilicate. Such solutions are readily made by mixing in water a substance containing available chlorine and a soluble alkali metal disilicate. The chlorine-containing substances generally used for such purposes, and conveniently used in the practice of my invention, are the alkali or alkaline earth metal hypochlorites such as sodium hypochlorite (NaOCi) or bleaching powder, and such substances are to be preferred although other compounds may be used. In any case the solution should contain an amount of available chlorine sumcient to produce an effective sterilizing action. This amount may be,

in some cases, as low as one part per million, but generally it is greater than this, and where aluminum is to be sterilized the available chlorine is best present in amounts upward 'of 50 parts per million, thedesirable amount being between 5 about 50 and 500 parts per million. To l e chlorine-containing solution thus formed there is added such an amount of soluble alkali metal di-silicate as will achieve the desired effect. The amount added will depend upon the metalbeing treated and is readily determined by testing a small piece of the metal in the solution to determine whether or not the solution stains or corrodes the metal. In the case of sterilizing solutions designed for the treatment of aluminum, the amount of di-silicate present should 'be about 5 to 50 times the amount of available chlorine present, measured on the basis of parts per. million. In the usual case the addition to the solution of 10 to times as many parts of alkali 20 metal di-silicate as there are parts of available chlorine will achieve the desired result.

The solution may be prepared by any suitable method. The two compounds may be used in powdered form, having first been mixed together and then introduced together into the proper amount of water, 0; hey may be added separately, the order of addition-not being important.

The alkali metal di-silicate which is used should be water-soluble or substantially so, and while any alkali metal di-silicate meeting these' requirements is satisfactory, I prefer to use sodium di-silicate. The water-soluble sodium di-silicate which I prefer is one containing about 27.5 per 0 cent NazO and 55 percent Si02, the balance being water of hydration or combination.

Having thus described my invention, I claim: 1. A sterilizing solution for sterilizing aluminum articles comprising a water-soluble alkali 40 metal di-silicate and available chlorine.

2. A sterilizing solution for sterilizing alumi num articles comprising a water-soluble sodium di-silicate and available chlorine.

3. A sterilizing solution for sterilizing aluminum comprising a water-soluble alkali metal di-' silicate and .available chlorine, the alkali metal di-silicate being present in the solution in the ratio of 5 to parts to every part of free chlorine.

4. A sterilizing compound for sterilizing aluminum comprising sodium di-silicate and a compound which on dissolving in water produces available chlorine. V

5. sterilizing solution for sterilizing'aluminum articles comprising a'sodium silicate having a ratio of NazO to SiOz of 1:2, and available chlorine.

LAMONT J. BENSON. 

